In recent television broadcasting, extremely violent or obscene expressions are used in the contents of some of broadcasting programs, and extremely abusive conversation which cannot be put up with is made in a so-called variety program. Therefore, there is a growing tendency to restrict the viewing of the broadcasting programs as ones which are not preferable from the point of view of education of children.
Furthermore, in some of broadcasting channels, a program for adults is broadcast as a dedicated channel for adjusts, and viewing is restricted such that the program cannot be viewed unless a password is entered. The tendency to restrict viewing is particularly significant in the U.S. The 1996 Telecommunication Law which is a new telecommunication law was enacted during the term of office of President Clinton, and rating information related to a rating representing the degree of extremity of the contents of a program is forced to be superimposed on a television broadcasting signal and transmitted toward a broadcasting station. A television receiver that receives the television broadcasting signal is obliged to contain a viewing restricting function such that the restriction of viewing utilizing the rating information can be enforced.
Specifically, the rating information is superimposed on the television broadcasting signal in the 21-st horizontal scanning period (21H) of an odd field in a vertical blanking period on the side of the broadcasting station. The contents of the rating are illustrated in FIG. 27. The rating information is superimposed on the television broadcasting signal in the 21H of the odd field and sent at intervals of less than five seconds as data (packet data) in the form of a packet from the broadcasting station.
Of course, it is also possible to insert the rating information into a bit stream as a digital broadcasting signal.
On the other hand, the television receiver has, on the side of a receiver, that is, on the side of a user, a muting function for setting the viewing restriction level of a program which a guardian to a child does not desire the child to view by a viewing restricting function is set by a rating, not to normally reproduce a video and an audio when a program or a channel having a rating which is not less than the set viewing restriction level.
The muting function is also performed similarly with respect to a so-called picture-in-picture or a closed caption which is subtitle display broadcasting for people with hearing difficulties or for non-native speakers of English in the U.S.
The restriction of viewing is generally set and released through the entry of a password composed of a four-digit number or the like. FIG. 28 is a block diagram showing the configuration of a conventional television receiver having a viewing restricting function.
The television receiver comprises an antenna 51 for television broadcasting, a tuner 52, a controller 53, a video demodulator 54, an RGB processor 55, and a display 56. The tuner 52 frequency-converts a television broadcasting signal received by the antenna 51. The video demodulator 54 comprises a video intermediate frequency amplifier, a video detector, and so forth, and demodulates a high-frequency signal fed by the tuner 52 into a video signal. The RGB processor 55 converts the video signal fed from the video demodulator 54 into an RGB signal. The display 56 is constituted by a CRT (Cathode-Ray Tube), an LCD (Liquid Crystal Display), or the like, and displays the RGB signal fed from the RGB processor 55 as a video. The controller 53 controls the tuner 52, the video demodulator 54, and the RGB processor 55.
The operations of the television receiver shown in FIG. 28 will be described. Rating information is transmitted as packet data having a data transmission format shown in FIG. 29 from a broadcasting station. The packet data indicates a rating provided by an extended data service performed in North America.
A television broadcasting signal including rating information is received by the antenna 51, and is fed to the tuner 52. An arbitrary channel is selected by the controller 53. In the tuner 52, the television broadcasting signal on the channel selected by the controller 53 is frequency-converted. In the video demodulator 54, an output from the tuner 52 is demodulated, and is output to the RGB processor 55 as a video signal. In the RGB processor 55, the video signal is converted into an RGB signal for driving the display 56, and is output to the display 56. Consequently, a desired video is displayed on the display 56.
On the other hand, the video signal branched from the video demodulator 54 is inputted to the controller 53. In the controller 53, the rating information is extracted from the video signal.
FIG. 30 is a flow chart showing the processing of the controller 53 in the television receiver shown in FIG. 28. The controller 53 accepts packet data composed of 6 bytes, and extracts rating information from the third byte and the fourth byte of the packet data (step S201).
The controller 53 compares a rating represented by the extracted rating information with a rating previously set by the user, to judge whether or not viewing is restricted (step S202). The controller 53 restricts viewing when the set rating is not more than the extracted rating, to display a message on a screen of the display 56, and subjects the RGB processor 55 to muting processing, to set the display 56 to a deep black screen or a blue back screen, for example (step S203). When the set rating is higher than the extracted rating, the controller 53 sets the RGB processor 55 in a muting processing released state without restricting viewing, to display a video of a program on the display 56 (step S204).
In such a way, the rating of a program which a guardian to a child previously considers to be detrimental to mental health or culture of sentiments is set in the controller 53, thereby making it possible to prevent a program having a rating which is not less than the set rating from being displayed.
As described above, the viewing restricting function can be set and released by entering a password. The same is also described in JP-A-2000-354209 and JP-A-2001-16565. The former discloses that a time period during which the viewing restricting function is released is set, and the latter discloses that the viewing restricting function is not released when an external input is a nonstandard signal.
In the above-mentioned conventional television receiver, there is a case where the rating of a program which is broadcast cannot be previously recognized, it is not recognized that the program conforms to the restriction of viewing until the broadcasting of the program is started, and the user cannot view the program.
In a case where the user reserves the viewing of the program using an electronic program guide (EPG) or the like, the rating of a reserved program is not recognized until the program is broadcast in the conventional television receiver. When rating information extracted from a television broadcasting signal is not less than a rating previously set, therefore, the user cannot view the reserved program.
Conventionally, recording was thus unconditionally performed, and viewing was only restricted by the setting of the rating at the time of reproduction. However, there is a disadvantage in that a program whose viewing should be restricted is recorded. In this case, it is difficult to strictly restrict viewing at the time of reproduction. Therefore, it is preferable that the management of the restriction of viewing is unified on the side of the receiver at the time of recording, not to record a program having a rating which is not less than the set rating.
With respect to the ratings of programs which are currently broadcast in the U.S., for example, a television receiver of 13 or more inches is obliged to carry a so-called V-chip function for realizing a viewing restricting function.
However, the conventional television receiver carrying the V-chip function does not compare, until the time point where it receives rating information periodically transmitted in a program which is being currently broadcast, a rating represented by the received rating information with a rating previously set, to restrict viewing when the received rating is not less than the set rating. When the user switches a receiving channel, therefore, the viewing of a program having the rating which is not less than the set rating cannot be restricted until it receives the rating information.
FIG. 31 is a diagram showing in a time series an example of viewing restriction processing. As shown in FIG. 31, rating information R1, R2, R3, . . . , R6 on Channel 10 shall be transmitted in this order. Immediately after the rating information R1 on Channel 10 is transmitted, for example, when the user switches a receiving channel from Channel 8 to Channel 10, viewing is restricted at the time point where the rating information R1 is not accepted and the rating information R2 is accepted. In a time period T1 elapsed from the time point where the channel is switched until the rating information R2 is accepted, therefore, viewing is not restricted, so that a program is displayed. If a sending period of the rating information is five seconds, a program whose viewing is to be restricted is displayed for a maximum of five seconds.
Similarly, in a television receiver having a plurality of external signal input terminals and carrying a V-chip function, the viewing of a program is not restricted even if the program has a rating which is not less than a set rating until rating information is received in the case of switching from input of a plurality of external signals to input of a television broadcasting signal.
Furthermore, a television receiver having a key called a rapid chain (a rapid chain key) has been developed. The user presses the rapid chain key, thereby making it possible to perform an operation for alternately switching a first channel currently received and a second channel received immediately before the rapid chain key is pressed. In the case of the operation, when the rapid chain key is pressed in a predetermined period, each of the channels is switched immediately before rating information is received on the channel so that a V-chip function may, in some cases, be nullified.